targets: add support for GameBoy Advance

Only tested in an emulator (mGBA). Almost nothing is supported, but drawing to the screen works.
2026-08-21 12:59:04 +00:00 · 2019-08-01 15:25:09 +02:00
parent 9878f7ebc4
commit 9846c062b3
7 changed files with 301 additions and 0 deletions
@@ -0,0 +1,33 @@
+.section    .init
+.global     _start
+.align
+.arm
+
+_start:
+    b       start_vector
+    .fill   156,1,0                // Nintendo Logo Character Data (8000004h)
+    .fill   16,1,0                 // Game Title
+    .byte   0x30,0x31              // Maker Code (80000B0h)
+    .byte   0x96                   // Fixed Value (80000B2h)
+    .byte   0x00                   // Main Unit Code (80000B3h)
+    .byte   0x00                   // Device Type (80000B4h)
+    .fill   7,1,0                  // unused
+    .byte   0x00                   // Software Version No (80000BCh)
+    .byte   0xf0                   // Complement Check (80000BDh)
+    .byte   0x00,0x00              // Checksum (80000BEh)
+
+start_vector:
+    mov     r0, #0x4000000                 // REG_BASE
+    str     r0, [r0, #0x208]
+
+    mov     r0, #0x12                      // Switch to IRQ Mode
+    msr     cpsr, r0
+    ldr     sp, =__sp_irq                  // Set IRQ stack
+    mov     r0, #0x1f                      // Switch to System Mode
+    msr     cpsr, r0
+    ldr     sp, =__sp_usr                  // Set user stack
+
+    // Jump to user code (switching to Thumb mode)
+    ldr     r3, =main
+    bx      r3
+